Lock with changeable guard and locking keys

ABSTRACT

A two key lever tumbler lock with at least two sets of tumblers alignable to interfit respectively with at least two sets of combs. The combs move with the bolt, and the two tumbler sets must be aligned with them by the concurrent use of two keys, operating in opposite directions upon the two sets of tumblers, to permit withdrawing the bolt. When the bolt is extended the combs of the first and second sets are fixed with respect to it, but when the bolt has been withdrawn to a certain position, both sets of combs are freed so that their positions can be changed by the use of new keys that shift the combs by acting upon the tumblers with which the combs are respectively interfitted. Third sets of tumblers and combs may be provided, in order to require the use of a third or change key in place of one of the two regular keys, to move the bolt past the normal unlock position to a special change position.

United States Patent [1 1 Parrock LOCK WITH CHANGEABLE GUARD AND Inventor:

Assignee:

US. Cl 70/339, 70/355, 70/383 Int. Cl E05b 25/00, E05b 35/12 Field of Search 70/337, 339, 340,

References Cited UNITED STATES PATENTS 7/ 1926 Lewis 70/385 3/1933 Diesel 10/1931 Benham 70/385 Primary Examiner-Robert L. Wolfe Attorney-James S. Hight et al.

ii-CHANGE COMB a9- BOLT GUAR D COMB-i/ Nov. 20, 1973 [57] ABSTRACT A two key lever tumbler lock with at least two sets of tumblers alignable to interfit respectively with at least two sets of combs. The combs move with the bolt, and the two tumbler sets must be aligned with them by the concurrent use of two keys, operating in opposite directions upon the two sets of tumblers, to permit withdrawing the boltQWhen the bolt is extended the combs of the first and second sets are fixed with respect to it, but when the bolt has been withdrawn to a certain position, both sets of combs are freed so that their positions can be changed by the use of new keys that shift the combs by acting upon the tumblers with which the combs are respectively interfitted. Third sets of tumblers and combs may be provided, in order to require the use of a third or change key in place of one of the two regular keys, to move the bolt past the normal unlock position to a special change position.

12 Claims, 8 Drawing Figures JJ-CHANGEJUMBLER /J'-TUMBLER POST M-GUARD TUMBLE R w-cug weR coM E J 'PMENIEUNUYPQ 1975 3.772.904

SHEET 1c? 4 J5-CHANGE .TUMBLER lJ-TUMBL POST MER COMB SHEET LOCK WITH CHANGEABLE GUARD AND LOCKING KEYS This invention relates to lever tumbler locks of the type which requires use of two keys before the bolt can be withdrawn. More particularly, it relates to a key changeable lock of this type, wherein each of the two keys can be changed.

Locks of the two key type are widely used on safe deposit boxes, and for that reason the invention is described hereinafter primarily with reference to that use, although it should be recognized that the invention can be used in locks for other purposes.

Two key locks are useful for safe deposit boxes by reason of the fact that neither key alone can open them, and the conjoint use of two keys is required. One of the keys--commonly called a guard key, or a custodian key-is typically retained by the bank or other institution, and must be used by it before the box can be opened; the other key, commonly called a locking key or a customer key, is retained by the individual box renter or customer, and its use is also required. Thus, no customer can surreptitiously open a box without knowledge of the bank, and vice versa.

It is the general practice that many or all of the boxes in a given installation are operated by the same guard key so that the guard need carry only one key to operate the many boxes, rather than having to carry a different individual guard keys for each box. However, the customer keys will differ from box to box. Since a given box will from time to time be rented to a new customer, it is desirable to provide changeability of the customer key, and this is known in the art. Thus, when a particular box is rented to a new customer, the lock is changed so that it is operable by a different customer key which will be issued to the new customer, so that the previous customers key can no longer be used. A two key lock permitting changing of customer keys is shown in a U.S. Pat. to Edgar Benham, No. 1,826,595, issued Oct. 6, 1931, and assigned to the assignee of this application.

It has in the past been difficult to produce for inventory two key deposit box locks of the Benham type, since the number of boxes required to fit the same guard key is not generally known in advance. Large numbers of boxes are often required for a given installation, and where they are to be operated by a common guard key, usually they can be assembled only after an order for a specific quantity has been received. Similarly, where the boxes are to go in an existing installation which is already served by a standard guard key, information as to the nature of that guard key is required in advance before the lock can be manufactured to fit it. This has slowed the delivery of the locks, and in effect requires custom assembly for each particular installation, since the particular guard key with which they will be used is not known in advance.

Accordingly, it has been the principal objective of this invention to provide a lock of the two key type wherein both the customer key and the guard key can be changed, so that standardized boxes can be manufactured for inventory and subsequently set up to fit a particular customer key and a particular guard key upon installation and without disassembly.

Locks of the Benham type, which have been produced for many years, have permitted the guard key to be withdrawn from the lock after it has been inserted and has activated its tumblers, so that the lock can then once be operated by the customer key alone. While the Benham patent treats this as an advantage, it has proven to be disadvantageous in the respect that once the quard key has been used to set up the lock, when it is withdrawn the lock can later be opened by a customer without the actual knowledge of the guard unless the guard uses a separate key to deactivate the previously set-up tumblers. In effect, withdrawal of the guard key after the guard tumblers have preliminarily been set up converts the lock into a single key lock. Accordingly, it has been another objective of this invention to provide a two key lock wherein both the guard key and the customer key must be used simultaneously to operate the lock and wherein both keys must be in the lock the entire time the bolt is withdrawn.

In accordance with the invention, a lock is provided with a key shiftable bolt and at least two sets of combs or fences which are mounted on or movable with the bolt. Each comb is interfittable with a corresponding tumbler or blocking member. A first set of the tumblers is moved by a first key in a first direction of movement transverse to the direction of bolt movement, and a second set of the tumblers is operable by a second key in the opposite transverse direction. One of the first and second keys will constitute a customer key, and the other will constitute a guard key. When it is attempted to withdraw the bolt the first and second comb sets move with it but they will be arrested by the first and second tumbler sets so that bolt withdrawal is blocked unless the tumblers have been aligned by the first and second keys.

The lock also includes comb holding means which holds the combs in fixed transverse position with respect to the bolt when the bolt is in lock position, but which frees or releases the combs of the first and second sets (but no others, if there is a third set) for movement transverse to the bolt when the bolt is withdrawn and the keys are disengaged from the tumblers.

In accordance with the preferred embodiment of the invention, the bolt is movable from lock position to two withdrawn positions, one of which is the normal unlock position and the other of which is a special change position, for which a special change key is required. For this purpose, third sets of combs and tumblers are provided. All of the combs are mounted on or movable with the bolt between these positions. The first set of tumblers is moved by the first key in a first direction of movement transverse to the direction of bolt movement, and the second set of tumblers is operable by the second key in the opposite transverse direction. One of the first and second keys will constitute the customer key, and the other will constitute the guard key. The third set of tumblers constitutes change tumblers which are moved by a change key in one of the first and second directions-preferably in the same direction as whichever tumber set is operated by the guard keyand they are interfittable with the respective combs of the third set when aligned.

The first and second tumbler sets arrest the first and second comb sets only, unless the tumblers have been aligned by the first and second keys, and block movement of the bolt from the lock to the unlock position. The tumblers of the third set do not block movement of the bolt to the normal unlock position, but they do block movement to the change position unless they have been aligned with the third comb set by the change key.

In the preferred embodiment all of the combs are held in fixed transverse positions with respect to the bolt when the bolt is in lock position, but the comb holding means frees or releases the combs of the first and second sets only, for movement transverse to the bolt when the bolt is moved to the change position while the combs of the first and second comb sets are interfitted with the respective tumblers of the first and second tumbler sets. The tumblers of the first, second and third sets are all mounted on a common post, and are interleaved with one another. The keys are received in a single key post, which has two keyways or slots on diameterically opposite sides. A collar or mask around the nose of the key post prevents keys from being inserted into or removed from the keyways except when the bolt is in either the lock of the change position. The tumblers operated by the change and guard keys preferably reside on the same side of the key post, and are moved by those keys in one direction away from the key post; the tumblers operated by the customer key reside on the other side of the key post and are moved in the opposite direction away from the key post by the customer key. The transverse movability of the combs with respect to the bolt is provided by a post and slot mounting of the first and second comb sets. When the bolt is in lock position, the individual combs are held in specific transverse position by a pin or other element which is engaged in one of a series of transversely spaced slots on each comb. When the change key is used and the bolt is moved to change position, the combs are freed from the pin and their transverse positions with respect to the bolt can be changed by shifting the tumblers with which they are respectively interfitted.

The Benham patent previously referred to discloses a lock having first, second and third sets of tumblers which cooperate with first, second and third comb sets. However, only one of the keys, the customer key, is changeable, and only one of the sets of combs-the customer combs-is movable transversely with respect to the bolt for changing the positions at which the corresponding tumblers align with it. The guard combs of the Benham lock are rigidly mounted on the bolt; moreover the guard tumbers of Benhams lock interfit with means which hold them in set up position after the guard key has been operated, whereby the guard key is disadvantageously permitted to be removed from the lock before the bolt has been shifted to unlock position.

The invention can best be further described and understood by reference to the drawings wherein:

FIG. 1 is a diagrammatic exploded perspective view illustrating representative elements of a preferred form of lock constructed in accordance with the principles of the invention;

FIG. 2 is a plan view of a preferred form of lock in accordance with the invention, the lid having been removed, showing the lock with the bolt extended in lock position and the tumblers let down;

FIG. 3 is a fragmentary axial section taken on line 3-3 of FIG. 2;

FIG. 4 is similar to FIG. 2 but shows the lock when the guard and customer keys have been inserted and rotated to withdraw the bolt to unlock position;

FIG. 5 is a view similar to FIG. 4 but shows the lock set for changing the keys, the customer and change keys having been turned a full degrees and the combs freed to be set to new keys, and the bolt in change position;

FIG. 6 is a plan view of the assembled lock with the bolt in lock position, and the lid in place;

FIG. 7 is a diagrammatic axial section showing the manner in which the customer, change, guard and neutral keys coact with the respective tumblers of a preferred form of lock in accordance with the invention; and

FIG. 8 is a plan view of an alternative form of lock in accordance with the invention which does not include change tumblers or combs, and shows the lock with the bolt withdrawn, ready for new keys to be inserted.

GENERAL DESCRIPTION A general understanding of the elements of this lock and their operation can be gained by reference to the structure diagrammatically shown in FIG. 1. For simplicity, this figure shows only a single tumbler of each of the preferred three sets of tumblers, and the associated elements. A commercial lock in accordance with the invention will typically include several tumblers in each set, but the operation of the additional tumblers in each set is similar to the operation of those shown, to which they respectively correspond.

Referring to the simplified lock shown in FIG. 1, the lock includes a key-operated key post 10 which is rotatable about its axis. Key post 10 is journaled at its ends in a lock case and lid, not shown in FIG. 1 but described in detail subsequently. The key post has two keyways in the form of longitudinal slots or grooves 1 1 and 12, oriented 180 apart on its opposite sides. Slot 11 in use receives a locking or customer key, usually retained by a safety deposit box renter. Slot 12 receives a guard or custodian key, usually retained by the bank or guard. The customer key 76 has one or more lifts (see FIG. 7) spaced along its length in positions to engage a first set of tumblers, sometimes referred to as customer tumblers, one of which is designated at 13 in FIG. 1. Similarly, lifts are formed on the guard key to engage a second set of tumblers, called guard tumblers, one of which is shown at 14. Customer tumbler 13 and guard tumbler 14 are rotatable about a tumbler post 15 mounted in the lock case.

Each tumbler l3 and 14 is in the form of a lever, and has a gate or notch 16 or 17 respectively in the end opposite from post 15. Customer tumbler l3 swings about post 15 on one side of key post 10 (i.e., above the post in the drawing), and guard tumbler 14 swings on the other side of the key post (below it in FIG. 1). Since key slots 11 and 12 are diametrically opposite on key post 10, when the customer and guard keys respectively are inserted in them and turned clockwise in the drawing, a guard key lift will engage guard tumbler l4 and swing it in the direction around post 15 (counterclockwise in the figure, as shown by the arrow) which is opposite the direction that the customer key moves customer tumbler 13.

The keyed movements of the tumblers shift the respective gates 16 and 17 to positions at which they are aligned to receive or interfit with fingers 18 and 19 that project respectively from a customer fence, slider or comb 20 (which is one of a first comb set), and a guard comb 21 (which is one of a second comb set). Combs 20 and 21 are mounted to the bolt 29, being slidably engaged on a pair of comb posts 27, 28 that project perpendicularly from the bolt bar 32. The combs 20 and 21 are slidable on these posts transversely or crosswise to the direction of bolt movement, indicated by the arrow.

In the ordinary operation of the locki.e., when the keys are not being changed-the combs move in and out with the bolt between the lock and unlock bolt positions, and are prevented from shifting transversely on posts 27 and 28. Comb holding means in the form of a pin 41 passes through one of a series of laterally spaced slots, collectively designated at 40, in customer comb 20 and guard comb 21, and thereby fixes the transverse position of the bolt on each comb of the first and second comb sets. Pin 41 is fixed in the lock case and passes through a slot 42 in bolt bar 32. Thus, the lateral position of the comb fingers 18 and 19 with respect to the bolt is dependent upon the particular slot 40 in which pin 41 is engaged.

The gates 16 and 17 of the customer and guard tumblers must be aligned with the fingers 18 and 19 of the respective combs before bolt 29 can be withdrawn to unlock position. If any gate is not aligned, the respective finger will strike the end of the tumbler when it is attempted to withdraw the bolt, and the tumbler will block further bolt movement.

Keyed rotation of key post is transmitted to the bolt through a key bit or cam 31 on the key post. As the key post is turned, key bit 31 comes into camming engagement with bolt bar 32, and will shift the bolt toward unlock position (rightward in FIG. 1). The amount of bolt travelthe distance it is shifted to unlock position when the customer and guard key are inserted and turned-is limited by a third set of combs called change combs, one of which is designated at 33 in FIG. 1. The change comb is mounted on bolt posts 27, 28, and thus moves with the bolt. The change comb has a finger, as indicated at 34, which can interfit in a gate 36 in the end of a change tumbler 35 which is one of a third set of tumblers.

Change tumbler 35 is mounted on post for rotation about it and, similar to the guard tumbler, includes a keying surface which is engageable by a key inserted in key post slot 12. Gate 36 of change tumbler 35 will interfit with finger 34 of change comb 33 if but only if change tumbler 35 has been properly aligned.

Neither the guard key nor the customer key acts on the change tumbler, and when the lock is operated by use of those two keys, change tumbler 35 remains in a disaligned position with respect to change comb finger 34, and thereby limits the extent to which the key post can be turned and the amount the bolt can be withdrawn. By way of example, this may correspond to about 1 10 of key post rotation. The bolt travel in these circumstances is sufficient to unlock the lock, but it is not sufficient to permit the keys to be withdrawn.

However when, instead of the guard key, a change key is inserted in slot 12, and the customer key is operated in slot 11 of key post 10, then a lift on the change key will coact with change tumbler 35 to swing it about post 15 and bring gate 36 thereof into position to receive the finger 34 of the change comb. At the same time, another lift on the change key, corresponding to the respective lift on the guard key, will act upon guard tumbler l4 and align it. Thus, by use of the change key and the customer key together, all three of the tumblersthe customer tumbler, the guard tumbler, and the change tumblerwill*be aligned to receive the respective comb fingers. Then none of the tumblers will restrain bolt movement and the keys can be rotated further, for example to about This shifts the bolt to change position. When key post 10 is turned to this extent by the'concurrent use of the customer and change keys, combs 20 and 21 are moved with the bolt sufficiently far (to the right in FIG. 1) that the pin 41 becomes disengaged from comb slots40. When this occurs the transverse positions of the combs are no longer fixed with respect to the bolt. Their fingers 18 and 19 are engaged in the tumbler gates 16 and 17, and they can be shifted transversely (up or down) on the bolt by movement of the tumblers with which they are interfitted. With the key post in this fully rotated position, the key lifts are not engaging the tumblers, and the change and customer keys can be withdrawn. The tumbler biasing springs 44 and 45, acting through tumblers 13 and 14, hold combs 20 and 21 against the posts 28 and 27 respectively (see FIG. 5). A different locking key and a different guard key can be inserted in the respective key post slots. As this is being done the tumblers do not move since the keys have been turned to a position in which they are not engaged with the tumblers. When difierent customer and guard keys are inserted and turned back toward starting or lock position, their respective lifts engage the tumblers and swing them to new angular positions according to the heights of the lifts on the keys. As this occurs, the first and second tumblers correspondingly shift the first and second combs with which they remain engaged. Asthe keys are turned further, bit 62 cams bolt 32 leftward and pin 41 engages the particular comb slots 40 which have been aligned with it as the bolt is thrown to extended or lock position.

Pin 41 need not actually be engaged with the combs 20 and 21 at the unlock position (note FIG. 4, in which the pin is clear of the slots 40 at this position), because the combs are prevented from shifting at this bolt position by the keylifts acting through the tumblers with which the combs are engaged. When the bolt is moved toward the lock position, pin 41 thereafter holds the combs in positions which reflect the lift heights to which they are set.

SPECIFIC DESCRIPTION The elements of the lock are mounted in a hollow rectangular case 50 (see FIG. 3) having a bottom 51 and sidewalls around it. The case is closed by a lid 49 (see FIG. 6). Tumbler post 15 projects perpendicularly from case bottom 51 to which it is mounted at its inner end, and at its outer end receives a lid attachment screw 69. Openings 52 are provided in a lock case bottom 51 for securing the lock to the door of a safety deposit box, or to some other closure.

The key post 10 is journaled at its inner end in an aperture 54 in casebottom 51. The key slots 11 and 12 extend between the inner end of the key post and the flanged outer end or nose 55 (see FIG. 6). The key post nose 55 is surrounded by and joumaled in a cylindrical collar 56, which projects from lid 49 and which will extend through the closure to which the lock is mounted in use. This collar has an inturned rim or flange 57 which contains apertures 58 and 59 for key lifts at two diametrically opposite positions. These apertures will align with the key slots 11 and 12 when the key post is in the lock position shown in FIG. 2, in which the keys are parallel to the tumblers'keying surfaces, and do not engage any tumblers. The notches also align when the key post is in the change position (shown in FIG.

Bolt bit 31 is connected to key post at the inner end thereof, adjacent case bottom 51 (see FIG. 3). Customer key slot 1 1 preferably extends to this key bit, as indicated at 61 in FIG. 1. The radially extending nose or tip 62 of key bit 31 acts in camming relation on the side of an opening or cutout 63 in bolt bar 32. As shown in FIG. 3, the bolt bar is held adjacent case bottom 51 by a spacer 64, for sliding movement in a plane parallel to the case bottom.

Opening 63 in bolt bar 32, within which the key bit 31 is disposed, includes a cam follower surface 63 which is engaged by the nose 62 of the bolt bit as key post 10 is turned to the unlock position, suitably 110 degrees in the clockwise direction from the starting or lock position (see FIG. 4). Bolt block 66 is mounted at the outer end of bolt bar 32 and is movable through an opening 67 in the end wall of case 50 (FIG. 3).

The pin 41 which engages the slots 40 of the customer and guard combs and 21, as previously described, projects perpendicularly from case bottom 51 and passes through slot 42 in the bolt bar, and thus does not impede free bolt movement.

The comb posts 27 and 28 are mounted at their inner ends on the bolt bar and project perpendicularly from it, see FIG. 3.

The particular lock illustrated for purposes of explanation includes a first set of eight tumblers, which are the customer tumblers designated at ISA-H respectively. Between them are interleaved a second set of four tumblers, which are the guard tumblers 14A-D re spectively, and a third set of three change tumblers designated at 35A-C (see FIG. 7). The particular number, stacking order, and arrangement of the tumblers of the three sets is not critical to the invention, and may differ from what is shown; the number of course determines the number of possible key configurations. The customer tumblers 13A-l-I will generally be similar to one another, except that their respective gates 16 will generally be formed at different positions. The same applies to the guard tumblers. Moreover, the guard tumblers and the customer tumblers may be similar to one another, again except with respect to gate positions, although they need not be. However, the guard tumblers are oriented reversely from the customer tumblers on post 15, so that under the influence of the biasing spring 44 and 45 the different sets of tumblers 13 and 14 respectively will engage opposite sides of the key post 10, when in their let down positions. The customer tumbler bias springs 44 bear against the top wall of the lock case (as viewed in FIG. 2) and urge the respective tumblers counterclockwise toward the key post. The guard tumbler biasing springs 45, and the change tumbler biasing springs 46, all bear against the other or lower side wall of the case, and thus bias the respective tumblers clockwise, toward engagement with the key post 10 on the other side thereof, opposite to the customer tumblers. When the key post is in the lock or starting position, each tumbler is held by its biasing spring against the key post, and in this position the respective tumbler gates l6, l7 and 36 are scrambled, that is they are not aligned with the respective comb fingers 18, 19 and 34.

The customer combs or sliders 20 which comprise the first comb set, the guard combs 21 of the second comb set, and the change combs 33 of the third comb set are so stacked on the two posts 27 and 28 that they are in the same planes as. the respective customer tumblers, guard tumblers and change tumblers with which they coact. Individually they are designated by letters corresponding to the designations of their respective tumblers, thus, customer comb 20A cooperates with customer tumbler 13A, etc.

It should be observed that the customer combs 20 A-I-I and the guard combs 21 A-D are all slidable on posts 27, 28 in the direction transverse (i.e., perpendicular) to the direction of bolt movement, being slotted as at and 71 for this purpose. However, the change combs 33A-C are not movable on the posts on which they are mounted. It is this transverse shiftability which, as previously indicated, permits changing the relative positions of the customer and guard combs, thereby to change the positions to which the respective tumblers l3 and 14 must be moved in order to permit the bolt to be withdrawn.

In the preferred embodiment shown, each of the customer combs 20 A-l-l and each of the guard combs 21 A-D is provided with a series of four slots 40 spaced apart transversely in equal incremental amounts. The lifts on the keys are sized so that the lowest lift will move the tumbler on which it acts an amount sufficient to position the tumbler gate to receive the respective comb finger when pin 41 is engaged in the first or lowermost comb slot 40, and so forth.

As shown in the drawings, it is desirable to provide false gates in the form of shallow notches as designated at 72 and 73 on the tumblers 13 and 14 and on the tips of fingers 18 and 19, to confuse radiographic examination of the lock. These play no functional part in the operation of the lock, but are useful adjuncts to the other structure.

FIG. 7 shows the general type of customer key 76, guard key 77, change key 78 and neutral key 79 that can be used with the lock. Customer key 76 is inserted into customer key slot 11, with its lifts projecting outwardly in the planes of the respective customer tum blers 13 A-H. The key lifts may be and are preferably slightly wider than the thickness of the tumblers with which they coact, to compensate for slight axial misalignment. The guard key 77 has lifts which are positioned to engage the guard tumblers 14 A-D. The keys may also have false lifts between the true lifts, for purposes of confusion. The change key 78 includes all of the same lifts as the guard key, so that it will operate the guard tumblers, and in addition it contains three other lifts which are positioned to align with and operate the change tumblers 35A-C. In other words, the change key will do the job of the guard key, but will also operate the change tumblers. Neutral key 79 contains no lifts and is simply shaped to enable the bolt to be withdrawn, without operating any of the tumblers, when the combs have been set at such positions that their fingers are aligned with the gates when the tumblers are in let down position.

When deposit boxes equipped with these locks are sent from the factory and are installed, prior to rental, the combs 20 and 21 are positioned in the manner just described, so that they are in alignment with the tumbler gates 16 and 17 when the tumblers are in their let down positions, i.e., when not engaged by any lifts. This permits the bolt to be withdrawn without requiring any adjustment of the tumblers, by use of neutral key 79.

When inserted in slot 11 and turned, the neutral key merely turns bolt bit 62 and'withdraws the bolt. The bank official can thus unlock the box by means of the neutral key to exhibit the box to a prospective customer and thereafter may relock the box any number of times by means of the neutral key.

When a customer desires to rent the box, the customer and guard tumblers l3 and 14 are set up by inserting the desired customer key with simultaneous use of the desired guard key. The use of both these keys during setup enables the combs to be shifted to fit those particular guard and customer key lift positions. After the bolt is thrown and the customer and guard keys are withdrawn, then both the correct guard and customer keys must be used to withdraw it again. No key can be withdrawn except when the bolt is in either the lock or the change position, because at other positions the keys are not in alignment with the flange notches 58 and 59 and are trapped in the lock.

In the preferred lock just described, the special, separate change key 78 must be used to shift the bolt to the change position at which the combs are freed from fixed positions with respect to the bolt and the new keys can be inserted. This is advantageous for many situations, where very close control over key changes is desired. However, the inclusion of the change tumblers reduces the number of the guard and/or locking keys to which the lock can be fitted (for a lock having the same total number of tumblers). Moreover, a special or separate change key may not be needed or desired in all cases.

The alternative lock embodiment illustrated in FIG.

8 is provided to satisfy the latter objectives. It does not require a change key, and it permits the locking and/or guard keys to be changed when the bolt has merely been withdrawn by use of the current guard and locking keys. It also can accept a greater number of different guard keys, because the number of guard tumblers is increased by substituting additional guard tumblers for the change tumblers of the previously described embodiment.

The lock of FIG. 8 includes customer and guard tumblers and combs similar to those already described (corresponding elements are designated by the same numbers, preceded byv 1; thus the customer tumblers are 113A, etc.). The tumblers 113 and 114 are operated by a guard key 177 and a customer key 176, but no change tumblers or combs are provided. In place of the three change tumblers 35A-C and change combs 33A-C, three additional guard tumblers and combs are provided, which may be generally similar to the other guard tumblers and combs. As shown in FIG. 8, with the guard and customer keys alone, post 110 can be turned 180 to a position at which the keys are disengaged from the tumblers and the respective combs are freed from pin 141. The keys can then be removed and new keys inserted. In this embodiment there need be no separate or distinct change position, apart from the unlock position to which the bolt is withdrawn.

Those skilled in the art will appreciate that the invention can be incorporated in two bolt locks, having double bolt bits which move two bolts in different directions, rather than a single bolt. This and other embodiments are included in the scope of the following claims.

What is claimed is: 1. A two key lever tumble lock comprising,

a bolt movable from a lock position throughan unlock position to a change position,

first, second and third sets of combs movable with said bolt between said positions, 7

a first setof tumblers moved by a first key in a first direction of movement transverse to said bolt and respectively interfittable with the first set of combs when aligned therewith,

a second set of tumblers moved by a second key in a second direction of movement transverse to said bolt, opposite to said first direction, and respectively interfittable with the second set of combs when aligned therewith,

a third set of tumblers moved by a change key in one of the first and second directions, and respectively interfittable with the third set of combs when aligned therewith,

the first and second sets of tumblers blocking movement of said bolt from lock to unlock position unless they are respectively aligned with the first and second sets of combs,

said third set of tumblers not blocking movement of said bolt to unlock position but blocking movement thereof to change position unless they are respectively aligned with the third set of combs,

and comb holding means holding all of said combs in fixed transverse positions with respect to said bolt when said bolt is in lock position but freeing only the first and second sets of combs for movement transverse to the bolt when said bolt is moved to change position and the first and second sets of combs are respectively interfitted with the first and second sets of tumblers, the first and second sets of combs then being repositionable to respond to different first and second keys.

2. The lock of claim 1 which includes means preventing withdrawal of the first and second keys when said bolt is in unlock position.

3. The lock of claim 1 wherein the first, second, and third sets of tumblers are mounted for rotation about a common axis, and said first and second sets of tumblers reside on opposite sides of a key post in which said first and second keys are receivable.

4. The lock of claim 1 wherein said comb holding means comprises,

transversely spaced posts projecting from the bolt which are engaged in transversely extending slots in the first and second sets of combs so that the latter are shiftable transversely with respect to the bolt,

thefirst and second sets of combs each presenting a series of slots parallel to the direction of bolt movement but spaced transversely,

and a fixed member engaged'in said slots when said bolt is in lock position but disengaged from said slots when said bolt is in change position, the first and second sets of combs then being transversely shiftable with respect to the bolt.

5. The lock of claim 1 wherein each comb has a finger which is interfittable in a gate presented by the respective tumbler.

6. The lock of claim 1 wherein said first key is a customer key and said second key is a guard key.

7. The lock of claim 6 wherein the second and third sets of tumblers operate in the same direction of movement transverse to the bolt.

8. The lock of claim 1 wherein the third sets of combs and tumblers are sized to prevent said bolt from being shifted from unlock position to change position unless said first and second sets of tumblers are aligned with the respective first and second sets of combs.

9. The lock of claim 1 which includes a key post having two diametrically opposite keyways, one of which receives said first key and the other of which alternatively receives said second key and said change key.

10. The lock of claim 1 wherein the third set of combs engage the third set of tumblers and thereby block bolt movement from unlock to change position,

and means preventing removal of said first and second keys when said bolt is thus blocked.

11. A two key lever tumbler lock comprising,

a bolt movable between a lock position and a withdrawn position,

first and second sets of combs movable with said bolt between said positions,

a first set of tumblers moved by a first key in a first direction of movement transverse to said bolt and respectively interfittable with the first set of combs when aligned therewith,

a second set of tumblers moved by a second key in a second direction of movement transverse to said bolt, opposite to said first direction, and respectively interfittable with the second set of combs when aligned therewith,

the first and second sets of tumblers blocking movement of said bolt from lock to withdrawn position unless they are respectively aligned with the first and second sets of combs,

and comb holding means holding said combs in fixed transverse positions with respect to said bolt when said bolt is in lock position but freeing them for movement transverse to the bolt when said bolt is moved to withdrawn position with the combs interfitted with the respective tumblers, the first and second sets of combs then being repositionable to respond to different first and second keys.

12. The lock of claim 11 wherein said first and second sets of combs are mounted to the bolt for transverse movement with respect to it, said combs being held against such transverse movement by an element which engages them when said bolt is in lock position but which is disengaged from them when the bolt has been withdrawn to a predetermined position.

*0! =l l i 

1. A two key lever tumble lock comprising, a bolt movable from a lock position through an unlock position to a change position, first, second and third sets of combs movable with said bolt between said positions, a first set of tumblers moved by a first key in a first direction of movement transverse to said bolt and respectively interfittable with the first set of combs when aligned therewith, a second set of tumblers moved by a second key in a second direction of movement transverse to said bolt, opposite to said first direction, and respectively interfittable with the second set of combs when aligned therewith, a third set of tumblers moved by a change key in one of the first and second directions, and respectively interfittable with the third set of combs when aligned therewith, the first and second sets of tumblers blocking movement of said bolt from lock to unlock position unless they are respectively aligned with the first and second sets of combs, said third set of tumblers not blocking movement of said bolt to unlock position but blocking movement thereof to change position unless they are respectively aligned with the third set of combs, and comb holding means holding all of said combs in fixed transverse positions with respect to said bolt when said bolt is in lock position but freeing only the first and second sets of combs for movement transverse to the bolt when said bolt is moved to change position and the first and second sets of combs are respectively interfitted with the first and second sets of tumblers, the first and second sets of combs then being repositionable to respond to different first and second keys.
 2. The lock of claim 1 which includes means preventing withdrawal of the first and second keys when said bolt is in unlock position.
 3. The lock of claim 1 wherein the first, second, and third sets of tumblers are mounted for rotation about a common axis, and said first and second sets of tumblers reside on opposite sides of a key post in which said first and second keys are receivable.
 4. The lock of claim 1 wherein said comb holding means comprises, transversely spaced posts projecting from the bolt which are engaged in transversely extending slots in the first and second sets of combs so that the latter are shiftable transversely with respect to the bolt, the first and second sets of combs each presenting a series of slots parallel to the direction of bolt movement but spaced transversely, and a fixed member engaged in said slots when said bolt is in lock position but disengaged from said slots when said bolt is in change position, the first and second sets of combs then being transversely shiftable with respect to the bolt.
 5. The lock of claim 1 wherein each comb has a finger which is interfittable in a gate presented by the respective tumbler.
 6. The lock of claim 1 wherein said first key is a customer key and said second key is a guard key.
 7. The lock of claim 6 wherein the second and third sets of tumblers operate in the same direction of movement transverse to the bolt.
 8. The lock of claim 1 wherein the third sets of combs and tumblers are sized to prevent said bolt from being shifted from unlock position to change position unless said first and second sets of tumblers are aligned with the respective first and second sets of combs.
 9. The lock of claim 1 which includes a key post having two diametrically opposite keyways, one of which receives said first key and the other of which alternatively receives said second key and said change key.
 10. The lock of claim 1 wherein the third set of combs engage the third set of tumblers and thereby block bolt movement from unlock to change position, and means preventing removal of said first and second keys when said bolt is thus blocked.
 11. A two key lever tumbler lock comprising, a bolt movable between a lock position and a withdrawn position, first and second sets of combs movable with said bolt between said positions, a first set of tumblers moved by a first key in a first direction of movement transverse to said bolt and respectively interfittable with the first set of combs when aligned therewith, a second set of tumblers moved by a second key in a second direction of movement transverse to said bolt, opposite to said first direction, and respectively interfittable with the second set of combs when aligned therewith, the first and second sets of tumblers blocking movement of said bolt from lock to withdrawn position unless they are respectively aligned with the first and second sets of combs, and comb holding means holding said combs in fixed transverse positions with respect to said bolt when said bolt is in lock position but freeing them for movement transverse to the bolt when said bolt is moved to withdrawn position with the combs interfitted with the respective tumblers, the first and second sets of combs then being repositionable to respond to different first and second keys.
 12. The lock of claim 11 wherein said first and second sets of combs are mounted to the bolt for transverse movement with respect to it, said combs being held against such transverse movement by an element which engages them when said bolt is in lock position but which is disengaged from them when the bolt has been withdrawn to a predetermined position. 